Continuous process plants continuously process input components to produce output components. An oil refinery is an example of a continuous process plant. An oil refinery (or petroleum refinery) is an industrial plant where crude oil is processed and refined into more useful products, such as gasoline and other fuels. Oil refineries are typically large, high-throughput plants. Oil refineries typically utilize an enormous amount of complex equipment and employ many workers to operate and maintain the equipment. The profits of an oil refinery are closely tied to the amount of oil that is refined. The amount of oil, typically measured in barrels, varies from day to day and depends on many different variables including how well the equipment performs on a given day, as well as how well the employees perform on that same day.